1. Field of the Invention
The present invention relates to a method of producing a seat reclining apparatus which is installed in a seatback-angle adjustable reclining seat.
2. Description of the Related Art
A type of reclining apparatus including: a base plate (lower arm) which is fixed to one of a seat cushion frame and a seatback frame; a ratchet plate (upper arm) which is fixed to the other of the seat cushion frame and the seatback frame and provided on the inner periphery thereof with an annular internal gear (toothed portion); and pawls (a plurality of pawls are often provided at different positions in the circumferential direction) which are supported to be movable relative to the base plate in radial directions of the base plate, wherein the reclining seat is brought into a locked state, in which the ratchet plate and the base plate are prevented from rotating relative to each other, by bringing the outer toothed portion which is formed on each pawl into mesh with the annular internal gear of the ratchet plate, is widely known in the art as a seat reclining apparatus provided between a seat cushion side frame and a seatback side frame of a reclining seat.
More specifically, each pawl can move between an engaged position in which the outer toothed portion of the pawl is engaged with the internal gear of the ratchet plate and a disengaged position in which the outer toothed portion of the pawl is disengaged from the internal gear of the ratchet plate. A rotational member which can be rotationally operated is supported on the base plate, and a rotational force of the rotational member is converted into a radial force via a cam or the like to be transmitted to each pawl to move each pawl between the engaged position and the disengaged position. The seat reclining apparatus is provided with a biaser which biases the rotational member in a direction (locking direction) to move each pawl to the engaged position, and the locked state in which each pawl (the outer toothed portion thereof) and the ratchet (the internal gear thereof) are engaged is retained by the biasing force of the biaser in a state where the rotational member is not operated from the outside. Rotating the rotational member against the biasing force of the biaser causes each pawl to move to the disengaged position, thus allowing the reclining seat to move to an unlocked state.
A type of seat reclining apparatus in which spring members serving as biaser that provides a biasing force for bringing a reclining seat to a locked state (such as the aforementioned locked state) are arranged in an internal space between a base plate and a ratchet plate is known in the art (this type of seat reclining apparatus is disclosed in, e.g., Japanese Unexamined Patent Publication No. 2013-132348). In this type of seat reclining apparatus, it is difficult to install the spring members into the internal space from the outside after the base plate and the ratchet plate are combined. Therefore, the seat reclining apparatus is often produced by mounting each pawl and the spring members onto the base plate at a stage before the installation of the ratchet plate to the base plate, and thereafter installing the ratchet plate to the base plate to close the internal space.
When the ratchet plate is installed to the base plate, each pawl is brought closer toward the disengaged position than the engaged position in order to be prevented from interfering with the ratchet plate. In the type of seat reclining apparatus in which biasing spring members are installed before the installation of the ratchet plate, the spring members are already in an operating (biased) state at this stage, enabling the biasing force thereof to act, which causes a load against bringing each pawl closer toward the disengaged position than the engaged position. Additionally, when installing the spring members, there is a problem with each resiliently deformed spring member easily coming off due to a load being exerted on each spring member in a state where a side thereof is not covered by the ratchet plate. Accordingly, the following series of operations are required: an operation to install each spring member while holding each spring member from one side so as not to come off, an operation to move each pawl toward the disengaged position (to move the rotational member in the unlocking direction) against the biasing force of the associated spring member and then an operation to install the ratchet plate to the base plate, which is troublesome. In other words, the degree of difficulty in assembling the seat reclining apparatus is high.